To provide a power supply device efficiently detecting a voltage drop without measuring a supply voltage inside complicated electronic equipment.

This power supply device includes: a voltage source; a connection means for connecting the voltage source and a load; a voltage difference detection means for detecting a difference value between a first voltage value at a first voltage measuring point between the voltage source and the connection means and a second voltage value at a second measuring point between the connection means and the load; and a comparison calculation circuit which determines that abnormality has occurred when the difference value is out of an appropriate range.